Optical matrix switches are commonly used in communications systems for transmitting voice, video and data signals. Generally, optical matrix switches include multiple input and/or output ports and have the ability to connect, for purposes of signal transfer, any input port/output port combination, and preferably, for N.times.N switching applications, to allow for multiple connections at one time. At each port, optical signals are transmitted and/or received via an end of an optical fiber. The fiber ends of the input and output ports are optically connected across a switch interface. In this regard, for example, the input and output fiber ends may be physically located on opposite sides of a switch interface (for direct or folded optical pathway communication therebetween), in side-by-side matrices on the same physical side of a switch interface facing a mirror, or may be interspersed in a single matrix arrangement facing a mirror.
Establishing a connection between a given input port fiber end and a given outport fiber end, involves configuring an optical pathway across the switch interface between the fiber ends. One way to configure the optical pathway is by moving or bending the optical fibers using, for example, piezoelectric benders. The benders associated with fibers to be connected bend the fibers so that signals from the fibers are targeted at one another so as to form the desired optical connection across the switch interface. The amount of bending is controlled based on the electrical signal applied to the benders. By appropriate arrangement of benders, two-dimensional targeting control can be effected. Another way of configuring the optical path between an input fiber and an output fiber involves the use of one or more moveable mirrors interposed between the input and output fibers. In this case, the fiber ends remain stationary and the mirrors are used for switching. The mirrors can allow for two-dimensional targeting to optically connect any of the input port fibers to any of the output port fibers.
In order to provide accurate targeting and alignment control, optical switch systems may employ control signals for servo-control. For example, a number of LEDs may be positioned in known locations around each fiber in the fiber array, and at least one control signal detector may be provided in connection with each fiber. Target identification can then be accomplished by lighting the LEDs in a pattern of rows and columns to identify a target fiber. Optimizing the alignment of connected fibers involves using the LEDs as alignment beacons and employing the detector outputs for closed-loop alignment control.